For this achievement you want to load up challenge 3 and follow the 3 videos below. There are 3 videos because some people have a lot of trouble with this so i made 3 ways to get it just in case 1 or 2 videos dont work for you.

The right lane is the fastest way but could take multiple attempts and is all about luck. The left lane guides take about 10-20 seconds longer but are more effective and the second left lane video seems to be more effective than the first but all 3 videos work.

If you get any enemies that have armor on during one of your runs then its best to just get eaten by zombies since theres no restart button.

Ill leave the video below and a written version of it below the video

Theres 3 ways to get this achievement1) The Left Lane has 2 versions

You must Grab the sten gun and 2 ammo packs and then go through the left and grab the meat and then throw it in a spot where it will distract all the zombies and then kill the bomber on the dock and put in the spark plugs. Sometimes it doesn't let you put the spark plug in because it says theres zombies around which is the only thing that can mess this up

2) The Right Lane (WeighingBrutes Method)

You must grab the sten gun and 2 ammo packs stick to the right side and kill the 3 or 4 zombies and then proceed to the dock and kill the bomber then put in the spark plugs

If you wanted to you could go to the right lane and kill the zombies and the bomber, then grab the meat and throw it so you can put in the sparkplugs without any zombies bothering you.

Hopes this helps pm me or comment if you have any questions or anything to add to the solution. If you give me a negative vote please comment or pm why so i can fix it.